Carburetor



July 11, 1967 s. TAYLOR 3,330,542

CARBURETOR Filed Nov. 22, 1965 A TTOR/VY United States Patent 3,330,542 CARBURETOR Roland S. Taylor, Fairport, N.Y., assignor to G eneral Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 22, 1965, Ser. No. 509,049 1 Claim. (Cl. 261-23) This invention relates to a carburetor in which the main well is continually refilled as fuel evaporates therefrom.

In a recently introduced multiple-stage carburetor, the primary stage meters fuel according to .a pressure signal created in a venturi and the second-ary stage meters fuel past a metering rod positioned by an air flow sensing valve. Under low speed, light load conditions of operation, the entire air flow is controlled by the primary stage and the entire fuel flow is metered in the primary stage, the secondary stage being required only for high speed or heavy load operation. In this carburetor, therefore, the metering rod which controls fuel flow in the secondary stage closes the metering orifice to prevent fuel flow when operation of the secondary stage is not required. Although the secondary metering rod does not actually seat in the orifice, it so closely approaches the orifice that the surface tension of the fuel is sufficient to prevent fuel flow through the orifice.

When subjected to conditions of high temperature, the

vfuel present in the secondary main well, downstream of the metering orice, tends to evaporate. Unless the evaporated fuel is replaced in the well, the carburetor may not function in the most desirable manner.

This invention provides a small opening extending from the fuel bowl into the main well permitting sufficient fuel flow to replace fuel evaporated from the secondary main well.

The details as well as other objects and advantages of this invention are disclosed in the following specification and in the drawing in which:

FIGURE 1 is a schematic sectional View through the primary and secondary stages of the carburetor illustrating the primary and secondary metering systems;

FIGURE 2 is an enlarged View of a portion of FIG- URE 1 illustrating the metering rod construction provided by this invention; and

FIGURE 3 is a sectional view along line 3--3 of FIG- URE 2 illustrating the disposition of the metering rod within the orifice.

Referring first to FIGURE 1, the schematically illustrated carburetor is -more fully illustrated and described in co-pending application Ser. No. 504,961, filed Oct. 24, 1965, in the names of E. A. Kehoe yand D. D. Stoltm-an. Therefore, its construction and operation will be herein described only to the extent necessary for an understanding of this invention.

Carburetor 10 includes a fuel bowl 12 in which a substantially constant level of fuel is maintained by a float and inlet valve mechanism 13. Fuel bowl 12 supplies fuel to a primary mixture conduit 14 and a secondary mixture conduit 16. Primary and secondary throttles 18 and 20 control flow through mixture conduits 14 and 16 and are sequentially operable so that low speed, light load operation is controlled entirely by the primary stage of the carburetor.

3,330,542 Patented July 11, 1967 ICC Fuel is delivered from fuel bowl 12 to primary mixture conduit 14 through a metering orifice 22, a fuel passage 24, and a delivery nozzle 26 which discharges into a venturi cluster 28. Fuel is delivered from fuel bowl 12 to secondary mixture conduit 16 through an orifice 30 past a metering rod 32 and through a main well 34 and a delivery nozzle arrangement 36.

An air valve 38 is secured to a shaft 40 extending through mixture conduit 16. A cam 42 is secured to shaft 40. Air valve 38 is responsive to air flow through mixture conduit 16, the angular position of air valve 38 indicating the rate of air fi-ow. Cam 42 drives a follower 44, pivotally mounted at 46, to position metering rod 32 within orifice 30. As air flow through mixture conduit 16 increases and air valve 38 opens wider, metering rod 32 is withdrawn from orifice 30 so that fuel flow is properly controlled in the desired relation to air flow.

As illustrated in greater -detail in FIGURES 2 and 3, when operation of the secondary lstage is not required, metering rod 32 closely approaches orifice 30 to prevent fuel flow therethrough. If during this period the carburetor is subjected to conditions of high temperature, the fuel existing in secondary main well 34 evaporates and reduces the level therein. Unless the proper level is maintained in secondary main well 34, improper functioning of the carburetor may occur as the secondary stage is brought into operation. This invention therefore provides a radially extending slot 43 milled in metering lrod 32. Slot 48 passes through orifice 30 and need be only large enough to permit the slight rate of fuel ow necessary to replace evaporated fuel in secondary main well 34.

With this construction, the fuel level in the secondary main well is maintained at a predetermined level. Thus, fuel is discharged immediately when operation of the secondary stage is required. This construction therefore prevents a lag in discharge of fuel from the secondary nozzle and .assures a properly proportioned mixture of air and fuel as the secondary stage is brought into operation.

I claim:

An internal combustion engine carburetor including primary mixture conduit means, a secondary mixture conduit, means controlling said primary mixture conduit means and said secondary mixture conduit whereby the air ow for low speed light load operation is provided solely by said prim-ary mixture conduit means, an air valve rotatably disposed in said secondary mixture conduit, means controlling said air valve whereby its rotative position is responsive to and is a measure of the rate of air flow through said secondary mixture conduit, a fuel bowl, a fuel passage extending from said fuel bowl to said secondary mixture conduit, valve means comprising a metering orifice in said passage and a tapered metering rod reciprocable in said orifice to and from a first position to vary the effective opening of said orifice and control fuel flow through said orifice and into said passage, means positioning said metering rod in accordance with the rotative position of said airvalve whereby fuel flow is controlled in relation to air flow, wherein in said first position the periphery of said rod approaches said orifice sufficiently close to prevent fuel flow through said orifice and into said lpassage at a rate which would provide selfsufficient engine operation, and opening means extending from said fuel bowl to said fuel passage downstream of said lorifice permitting only sufficient fuel flow into said fuel passage to replace fuel evaporated therefrom, said 3 opening means being incapable of permitting sucient 2,362,145 11/ 1944 Mallory 261-69 X fuel flow into said fuel passage to provide self-suicient 2,501,060 3/ 1950 Lei'bing 261-69 X engine operatiOn- 2,675,792 4/ 1954 Brown et al 261-69 X References Cited 2,332,576 4/1953 Henning. UNITED STATES PATENTS 5 3,053,240 9/ 1962 Mick 261-69 X gg ggg; al; 261-"66 HARRY B. THORNTON, Primary Examiner.

1,579,600 4/1926 Durante. RONALD R. WEAVER, Examiner. 

